Automatic dishwashing, particularly automatic dishwashing in domestic appliances, is an art having important distinguishing features from superficially similar arts such as fabric laundering and institutional dishcare. For example, domestic fabric laundering is normally done in purpose-built machines having a tumbling action, quite distinct from spray-action domestic automatic dishwashing appliances. In domestic machine dishwashing, dishes need to be rendered clean, that is to say, for all practical purposes, to "have the soil completely removed". Decolorization of the soil, as in fabric bleaching, will not suffice. It is not clear that such cleaning action actually requires "bleaching" in the traditional laundry sense at all; on the other hand, some bleaching chemicals can, in certain circumstances, be desirable for cleaning dishware.
In contrast to typical institutional tableware, consumer glasses, dishware and flatware, especially decorative pieces, as washed in domestic automatic dishwashing appliances, are often susceptible to damage and can be expensive to replace. Typically, consumers dislike having to separate finer pieces and the obligation of washing these by hand and would prefer the convenience and simplicity of being able to lump all their tableware and cooking utensils into a single, automatic washing operation. Yet doing this as a matter of routine has not yet been achieved.
Because of these consumer demands and needs, ADD compositions are undergoing continual change and improvement. Additionally, environmental factors such as the desirability of providing ever-better cleaning results with less product, providing less thermal energy, and less water to assist the washing process, have driven the need for improved ADD compositions.
A recognized need in ADD compositions is to have present one or more ingredients which improve the removal of starchy food residues or starchy films from dishware, flatware, and glasses. Other than use of large quantities of water, heat, and time, the simplest approach to achieve this function is to use sodium hydroxide. However, strong alkalis like sodium hydroxide are potentially hazardous in a domestic setting and even can be damaging to, or leave a film upon, glasses or dishware. Accordingly, milder ADD compositions have been developed which typically incorporate amyolytic enzymes such as TERMAMYL.RTM. available from Novo Nordisk S/A. The alpha-amylase component provides at least some benefit in the starchy soil removal properties of the ADD. ADD's containing amylases typically can deliver a somewhat more moderate wash pH in use and can avoid delivering large weight equivalents of sodium hydroxide on a per-gram-of-product basis. However, often the amylases used in ADD compositions are those developed for use in quite different fields, such as fabric washing, textile desizing or even starch liquefaction and are not as effective as might be desired when used in dishwashing. There remains a substantial technical challenge in co-formulating essential ADD components such as amylase-compatible bleaches, sequestrants and surfactants in such a manner as to meet the consumer's need for superior cleaning performance at an excellent value in a safe, environmentally acceptable product which leaves the dishware, glasses and flatware in fine and undamaged condition. A need therefore exists for the development of amylase enzymes specifically designed to be compatible in ADD formulations.
Accordingly, manufacturers of enzyme preparations have lately been developing novel alpha-amylases, which at least in some tests, exhibit a greater or lesser degree of one or more technically measurable improvements. Examples of such improvements include providing new amylases which are more thermally stable, have a better temperature optimum for cold-fill, warm wash or warm-fill appliances, have a pH optimum better aligned with those now preferred for ADD's, or have a greater hydrolysis velocity for starches than the hydrolysis velocity exhibited by conventional alpha-amylases.
More particularly, and without being limited by theory, the currently commercial varieties of alpha-amylases, including those having improved bleach stability in certain tests, can exhibit an unpredictable range of stability and compatibility with the huge array of different possible bleaching or stain removing agents ranging from chlorinated isocyanurates, peroxidases and phthalocyanines, persulfates, perborates and di-organo peroxides, through to many hundreds of different types of bleach catalysts or "accelerators", preformed organic peracids and thousands of possible bleach activator chemicals. This is particularly true in fully-formulated detergent products. Despite ongoing and continuous research the richly varied array of bleach or stain-removal chemistry has not been reduced to a simple governing mechanism. In bleach chemistry, including the aspect of undesirable potential attack on enzymes as well as the desirable aspect of bleaching/cleaning soils, there are often many reaction steps to be considered.
In view of the foregoing considerations, it is apparent that there remains in the industry a need for improved ADD compositions, which on one hand contain amyolytic enzymes and on the other, compatibly provide stain removal or sanitizing technology, such as that derivable from certain bleaches. It is an object of the instant invention to provide such compositions without, since such stability advantages are limited, relying exclusively on bleach stability advantages of the new amylases.
In another aspect of the invention, it is an object herein to provide fully-formulated ADD compositions wherein the bleach/amylase combinations are combined with additional selected ingredients so as to deliver superior cleaning results at the same time as excellent dishcare.